fpga: of-fpga-region: Fail if any bridge is missing

fpga: of-fpga-region: Fail if any bridge is missing

When parsing the region bridge list from the "fpga-bridges" device tree
property, the of-fpga-region driver will silently ignore bridges which fail
to be obtained, for example due to a missing bridge driver or invalid
phandle.

This can lead to hardware issues if a region bridge stays coupled when
partial programming is performed.

Fail if any of the bridges specified in "fpga-bridges" cannot be obtained.

Signed-off-by: Romain Gantois <romain.gantois@bootlin.com>
Link: https://lore.kernel.org/r/20251127-of-fpga-region-fail-if-bridges-not-found-v1-1-ca674f8d07eb@bootlin.com
Reviewed-by: Xu Yilun <yilun.xu@intel.com>
Signed-off-by: Xu Yilun <yilun.xu@linux.intel.com>